Hi all

I have a 2004 TD4 Freelander that has done 138,000 and been a reliable car for the years I have owned, up until last week.

Scenario, came home from work, all as usual, no problems no over heating or anything unusual. Following day jumped in the TD4 and it failed to start.

The engine is turning over smoothly, no knocks or bangs etc and the, battery is fully charged, the fuel pump behind the real wheel is running and I have fuel under pressure on the common rail leading to the injectors.

During the start up sequence the fuel pump stops (around 45 seconds) as I assume the pressure sensor in the common rail has indicated to the engine control module (ECM) that sufficient pressure has been raised.

The engine heaters are coming on (one has failed but the other 3 are fine) as I tested them with my voltmeter 12v at the heater side of the heater relay and tested the heater resistances. The heaters come on for around 30 seconds followed by the dash heater light going out. So I assume the engine control module is sensing the coolant temperature which it uses to manage the heater electrical supply.

So as the engine was turning fine, and I had fuel to the common rail I checked the Crank Shaft Speed sensor and the Cam Shaft Speed sensor. I was not able to properly test the two sensors so I simply replaced them with new parts.

Following the sensor replacement the engine still fails to start.

I am wondering if the ECM is not controlling the injectors. How do I test that the injectors are being switched by the ECM ? Would I be able to measure say 12v pulsing to each injector as I turn the engine over ?

Electrically all the fuses are OK and the relays are working (took them out & tested them).

The ECM is a Bosch one, and the car has had a fuel rail pressure sensor wiring modification done, although not fitted with a new fuel rail pressure sensor. How can I test the fuel rail pressure sensor as that maybe sending wrong information to the ECM although I would have thought that would be a simple on or off and as its switching off the fuel pump is working OK ? Maybe ?

Anybody got any other ideas ?

Thanks guys, all help appreciated !

I think the prime sequence is just timed rather than reaching a pressure threshold. If the low pressure sensor doesn’t see enough pressure, the HP pump will be shut down to preserve it.

An OBD scanner might be useful here, but try some easystart. If it fires and keeps running, could be a leaky injector. Search ‘leakback test’.

Worth a check of the HP pump regulator O-ring (inside the module on the HP pump with an electrical connector).

Corroded rail pressure sensor contacts? I have a feeling this won’t prevent starting, but easy to check.

We really need a ‘Td4 won’t start’ sticky.

EDIT: re injector pulse testing. I’ve not done this, but you might be able to back-probe the injector plugs with a test light.

Wot was said above /\

The lift pump in the rear wheel arch could never generate the pressure needed for the injectors to properly inject the fuel into the cylinders. The injectors need a lot of pressure to get the fuel injected in a fine mist in the correct place in the cylinders for them to fire efficiently. The pump might or might not result in some pressure in the rail (depending on how the high pressure pump is designed) - but the pressure sensor in the rail is not there to measure that. It is there to measure the pressure generated by the high pressure mechanical pump attached to, and driven by, the engine. There is a separate pressure sensor to determine the pressure the lift pump is providing to the high pressure pump.

The Cam and Crank sensors do not test for speed, they test for the engine's position (eg angle from TDC). Knowing where the pistons are is what the ECU uses to time its communication with the injectors (together with its other inputs). They may, secondarily, be used by the ECU to calculate the engine's speed as this is also used to limit how much fuel is injected and possibly override your throttle request.

Hi
I fitted replacement O rings the HP pump sensor at the back of the HP fuel pump.

The engine started and ran for a good 20 minutes until I turned it off. I then tried restarting it and after a a short period it started but the engine was not revving smoothly.

I stopped the engine and then tried restarting it...again a while before it started and it did not rev smoothly.

The HP fuel pump fitted to the car looks as though it is a replacement, although no signs of leaks..
I am beginning to think that the problem is either the HP fuel pump or the sensor at the rear of the HP fuel pump....or I didn't fit the O Rings correctly....it was difficult to reassemble (I had to push the sensor quite firmly and it only landed properly when I tightened up the two retaining Torx bolts).

What do you think ?

MW1LCR said:

I am beginning to think that the problem is either the HP fuel pump or the sensor at the rear of the HP fuel pump....or I didn't fit the O Rings correctly.

Click to expand...

There isn't a sensor on the HP pump, just the pressure regulator. Its seals can split, which stops the rail pressure building.

MW1LCR said:

.it was difficult to reassemble (I had to push the sensor quite firmly and it only landed properly when I tightened up the two retaining Torx bolts).

Click to expand...

As long as the seals aren't damaged, there's little else to go wrong.

The engine starts & runs but won't rev smoothly above 2500 RPM. It did rev smoothly beforehand. I will refit the O rings in case I messed that up.

Any other ideas ? I suppsoe if teh fuel pump supplies fuel at sufficient pressure the pump is OK, and the problem could well be something between the fuel pump and injectors blocking the supply ?

Have you checked the basics like the rail sensor and it's wiring?

The wiring to the common rail sensor was changed last year. The sensor itself was not changed at the time. The connections seemed OK but I will check again tomorrow.
How do I test the pressure sensor....

MW1LCR said:

The connections seemed OK but I will check again tomorrow.

Click to expand...

Check the terminals for corrosion.

MW1LCR said:

How do I test the pressure sensor.

Click to expand...

You can check the live data, if you have access to a code reader.

exactly whats happening to mine keeps coming up with p0201-p0204 injector circuit/open-cylinder 1-4 when we erase the codes start up runs over 2000 revs cuts out plug scanner in these codes come on again me and the mechanic are both baffled